Human Metapneumovirus (hereinafter hMPV) is the etiological agent of a representative percentage of hospitalization and morbidity associated with acute respiratory diseases of the upper and lower respiratory tracts, especially in infants, elderly and immunocompromised individuals. This virus infection is associated with a wide range of pathologies, being bronchiolitis and pneumonia the conditions with a higher socio-economic impact. HMPV infection has been associated with gastroenteritis and keratoconjunctivitis. For example, Calvo et al. (2008) demonstrated over a period of 3 years that cumulative incidence of acute respiratory infections caused by respiratory viruses: respiratory syncytial virus (RSV), adenovirus (ADV) and hMPV accounted for 64.5% of hospital admissions of children younger than 2 years, being the incidence for each virus 35.4%, 19.3% and 9.8%, respectively. One interesting feature that hMPV shares with the other high-incidence respiratory viruses is the production of repeated infections throughout childhood, a phenomenon possibly associated with a failure to establish a protective immune response to the first infection during the first few months of life. To date, there are no studies about the specific economic impact of hMPV infection, however, the incidence of hospitalization for hMPV has been estimated to be ⅓ of the incidence of hospitalization for human respiratory syncytial virus (hRSV). Studies carried out in developed countries estimate that the individual cost of hRSV infection is over 3,000 euros ($1.86 million Chilean pesos) with an upper limit of up to 8,400 euros ($5.2 million Chilean pesos). The costs associated to individual hospitalization are approximate and based on a pathological process of similar features that requires hospitalization
Although, hMPV and hRSV virus are grouped within the Metapneumovirus and pneumovirus genera, respectively, hMPV virus is classified in the Paramyxoviridae subfamily Pneumovirinae, the same family where hRSV is classified. hMPV genome comprises a non-segmented, single-stranded, negative-sense ribonucleic acid (ssRNA), so viral proteins are arranged in a 3′ to 5′ direction (relative to their sequence) as follows: N, P, M, F, M2 (ORF1 and ORF2), SH, G and L. Five of these proteins are responsible for packaging the genetic material and define the structure of the viral particle, corresponding to the nucleocapsid protein N and the matrix protein M, together with transmembrane glycoproteins F, G and SH, respectively. The other four proteins, M2-1, M2-2, P and L, are involved in viral replication and transcription. There are two subtypes of hMPV, classified as two antigenic groups A and B based on the sequence differences mainly found in the F and G proteins. Although these proteins have some degree of difference, there is a high identity compared to other proteins encoded by the viral genome.
HMPV detection is currently made using three techniques: RT-PCR, which amplified segments of the F and N genes directly from nasopharyngeal swabs samples, respiratory panel (direct immunofluorescence method routinely used in clinical laboratories, which allow simultaneous identification of different types of respiratory viruses) and in vitro culture in LLC-MK2 cells in order to detect a cytopathic effect. These techniques have a sensitivity not greater than 70% and both produce discordant results. One of the problems generated by low sensitivity and discordance between these techniques relates to the fact that respiratory infections negative for the respiratory panel are generally treated with antibiotics to avoid possible bacterial superinfections. Thus, false negative currently delivered by the available techniques are not receiving appropriate treatment and the patient is exposed to unnecessary antibiotic treatment, which further increases the possibility of generating antibiotic resistance in said patient.
Therefore, it is essential to have an effective and rapid diagnostic test for hMPV. Due to this problem, the monoclonal antibodies of the invention appear as a necessary alternative to fulfill this need, since they allow specific recognition of viral antigens in samples from patients infected with hMPV. Thus the present invention includes products such as monoclonal antibodies, and an alternative method that makes use thereof for accurate, effective and rapid detection and diagnosis in patients infected with hMPV with 100% specificity in clinical samples and capable to detect concentrations equivalent to 1.5 ng of the specific antigen by ELISA. This will allow clinicians to implement an early and appropriate treatment that could anticipate the disease course.